Cathode active material, its manufacturing method, and non-aqueous electrolyte secondary battery

Abstract

A cathode active material is provided. The cathode active material includes: a composite oxide particle including at least lithium and cobalt; a coating layer which is provided in at least a part of the composite oxide particle and includes an oxide including lithium and a coating element of at least one of nickel and manganese; and a surface layer which is provided in at least a part of the coating layer and includes at least one element selected from the group consisting of silicon, tin, phosphorus, magnesium, boron, zinc, tungsten, aluminum, titanium, and zirconium.

The invention is claimed as follows: 
     
         1 . A cathode active material comprising:
 a composite oxide particle comprising at least lithium and cobalt;   a coating layer which is provided in at least a part of said composite oxide particle and includes an oxide including lithium and a coating element of at least one of nickel and manganese; and   a surface layer which is provided in at least a part of the coating layer and includes phosphorus.   
     
     
         2 . The cathode active material according to  claim 1 , wherein mean compositions of the composite oxide particle are expressed by Formula 1,
   Li (1+x) Co (1−y) M y O (2−z)   (Formula 1)
   in Formula 1, M denotes an element of at least one kind selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, tin, and tungsten; x indicates a value within a range of −0.10≦x≦0.10; y indicates a value within a range of 0≦y<0.50; and z indicates a value within a range of −0.10≦z≦0.20.   
     
     
         3 . The cathode active material according to  claim 1 , wherein a construction ratio of said nickel and said manganese in said coating layer ranges from 100:0 to 30:70 as a mole ratio. 
     
     
         4 . The cathode active material according to  claim 1 , wherein the oxide in said coating layer is an oxide obtained by replacing 40 mol % or less of a total amount of said nickel and said manganese with a metal element of at least one kind selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, and tungsten. 
     
     
         5 . The cathode active material according to  claim 1 , wherein an amount of said coating ranges from 0.5 weight % to 50 weight % of said composite oxide particle. 
     
     
         6 . The cathode active material according to  claim 1 , wherein a mean diameter ranges from 2.0 μm to 50 μm. 
     
     
         7 . A method of manufacturing a cathode active material, comprising:
 forming a layer made of a hydroxide containing nickel and/or manganese into at least a part of a composite oxide particle including at least lithium and cobalt and, thereafter, coating at least a part of said composite oxide particle with a phosphoric acid; and   executing a heating process after coating with the phosphoric acid, thereby forming a coating layer made of an oxide containing lithium and a coating element of at least one of nickel and manganese and a surface layer containing phosphorus into at least a part of said composite oxide particle.   
     
     
         8 . The method of manufacturing the cathode active material according to  claim 7 , wherein mean compositions of said composite oxide particle are expressed by Formula 1,
   Li (1+x) Co (1−y) M y O (2−z)   (Formula 1)
   in Formula 1, M denotes an element of at least one kind selected from a group containing magnesium, aluminum, boron, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, tin, and tungsten; x indicates a value within a range of −0.10≦x≦0.10; y indicates a value within a range of 0≦y<0.50; and z indicates a value within a range of −0.10≦z≦0.20.   
     
     
         9 . The method of manufacturing the cathode active material according to  claim 7 , wherein said hydroxide including nickel and/or manganese is formed by
 dispersing said composite oxide particle into a solvent constructed mainly by water whose pH is equal to 12 or more and, thereafter, adding a compound of nickel and/or a compound of manganese.   
     
     
         10 . The method of manufacturing the cathode active material according to  claim 9 , wherein said solvent constructed mainly by the water contains lithium hydroxide. 
     
     
         11 . The method of manufacturing the cathode active material according to  claim 7 , wherein a construction ratio of the nickel and the manganese in the coating layer ranges from 100:0 to 30:70 as a mole ratio. 
     
     
         12 . The method of manufacturing the cathode active material according to  claim 7 , wherein the oxide in said coating layer is an oxide obtained by replacing 40 mol % or less of a total amount of said nickel and said manganese with a metal element of at least one kind selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, and tungsten. 
     
     
         13 . The method of manufacturing the cathode active material according to  claim 7 , wherein an amount of the coating layer ranges from 0.5 weight % to 50 weight % of the composite oxide particle. 
     
     
         14 . The method of manufacturing the cathode active material according to  claim 7 , wherein a mean diameter of the particle in said cathode active material ranges from 2.0 μm to 50 μm. 
     
     
         15 . A non-aqueous electrolyte secondary battery comprising:
 a cathode having a cathode active material;   an anode; and   an electrolyte, wherein   the cathode active material includes:   a composite oxide particle including at least lithium and cobalt;   a coating layer which is provided in at least a part of the composite oxide particle and includes an oxide containing lithium and a coating element of at least one of nickel and manganese; and   a surface layer which is provided in at least a part of the coating layer and includes phosphorus.